The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art to the presently claimed invention, or relevant, nor that any of the publications specifically or implicitly referenced are prior art.
The exendins are peptides that are found in the salivary secretions of the Gila monster and the Mexican Beaded Lizard, reptiles that are endogenous to Arizona and Northern Mexico. Exendin-3 [SEQ. ID. NO: 1: His Ser Asp Gly Thr Phe Thr Ser Asp Leu Ser Lys Gln Met Glu Glu Glu Ala Val Arg Leu Phe Ile Glu Trp Leu Lys Asn Gly Gly Pro Ser Ser Gly Ala Pro Pro Pro Ser-NH2] is present in the salivary secretions of Heloderma horridum (Mexican Beaded Lizard), and exendin-4 [SEQ. ID. NO. 2: His Gly Glu Gly Thr Phe Thr Ser Asp Leu Ser Lys Gln Met Glu Glu Glu Ala Val Arg Leu Phe Ile Glu Trp Leu Lys Asn Gly Gly Pro Ser Ser Gly Ala Pro Pro Pro Ser-NH2] is present in the salivary secretions of Heloderma suspectum (Gila monster) (Eng, J., et al., J. Biol. Chem., 265:20259-62, 1990; Eng, J., et al., J. Biol. Chem., 267:7402-05, 1992). The amino acid sequence of exendin-3 is shown in FIG. 1. The amino acid sequence of exendin-4 is shown in FIG. 2. Exendin-4 was first thought to be a (potentially toxic) component of the venom. It now appears that exendin-4 is devoid of toxicity, and that it instead is made in salivary glands in the Gila monster.
The exendins have some sequence similarity to several members of the glucagon-like peptide family, with the highest homology, 53%, being to GLP-1[7-36]NH2 [SEQ. ID. NO. 3] (Goke, et al., J. Biol. Chem., 268:19650-55, 1993). GLP-1[7-36]NH2, also sometimes referred to as proglucagon[78-107] or simply “GLP-1” as used most often herein, has an insulinotropic effect, stimulating insulin secretion from pancreatic beta-cells; Glucagon-like peptide-1 (GLP-1) has also been reported to inhibit glucagon secretion from pancreatic alpha-cells (Ørsov, et al., Diabetes, 42:658-61, 1993; D'Alessio, et al., J. Clin. Invest., 97:133-38, 1996). GLP-1 has been reported to inhibit gastric emptying (Willms B, et al., J Clin Endocrinol Metab 81 (1): 327-32, 1996; Wettergren A, et al., Dig Dis Sci 38 (4): 665-73, 1993), and gastric acid secretion (Schjoldager B T, et al., Dig Dis Sci 34 (5): 703-8, 1989; O'Halloran D J, et al., J Endocrinol 126 (1): 169-73, 1997 Wettergren A, et al., Dig Dis Sci 38 (4): 665-73, 1993)). GLP-1[7-37], which has an additional glycine residue at its carboxy terminus, is reported to stimulate insulin secretion in humans (Ørskov, et al., Diabetes, 42:658-61, 1993). A transmembrane G-protein adenylate-cyclase-coupled receptor said to be responsible at least in part for the insulinotropic effect of GLP-1 has reportedly been cloned from a beta-cell line (Thorens, Proc. Natl. Acad. Sci. USA 89:8641-45, 1992). GLP-1 has been the focus of significant investigation in recent years due to its reported action on the amplification of stimulated insulin production (Byrne M M, Goke B. Lessons from human studies with glucagon-like peptide-1: Potential of the gut hormone for clinical use. In: Fehmann H C, Goke B. Insulinotropic Gut Hormone Glucagon-Like Peptide 1. Basel, Switzerland: Karger, 1997:219-33). 
Other reports relate to the inhibition of gastric emptying (Wettergren A, et al., Truncated GLP-1 (proglucagon 78-107-amide) inhibits gastric and pancreatic functions in man, Dig. Dis. Sci. 1993 April;38(4):665-73), inhibition of glucagon secretion (Creutzfeldt W O C, et al., Glucagonostatic actions and reduction of fasting hyperglycemia by exogenous glucagon-like peptide I(7-36) amide in type I diabetic patients, Diabetes Care 1996;19(6):580-6), and a purported role in appetite control (Turton M D, et al., A role for glucagon-like peptide-1 in the central regulation of feeding, Nature 1996 January;379(6560):69-72).
GLP-1 has also been reported to restore islet glucose sensitivity in aging rats, restoring their glucose tolerance to that of younger rats (Egan J M, et al., Glucagon-like peptide-1 restores acute-phase insulin release to aged rats, Diabetologia 1997 June;40(Suppl 1) :A130). However, the short duration of biological action of GLP-1 in vivo is one feature of the peptide that has hampered its development as a therapeutic agent. Various methods have been tried to prolong the half-life of GLP-1 or GLP-1(7-37), including attempts to alter their amino acid sequence and to deliver them using certain formulations (see, e.g., European Patent Application, entitled “Prolonged Delivery of Peptides,” by Darley, et al., publication number 0 619 322 A2, regarding the inclusion of polyethylene glycol in formulations containing GLP-1 (7-37)).
Pharmacological studies have led to reports that exendin-4 can act at GLP-1 receptors on certain insulin-secreting cells, at dispersed acinar cells from guinea pig pancreas, and at parietal cells from stomach; the peptide is also reported to stimulate somatostatin release and inhibit gastrin release in isolated stomachs (Goke, et al., J. Biol. Chem. 268:19650-55, 1993; Schepp, et al., Eur. J. Pharmacol., 69:183-91, 1994; Eissele, et al., Life Sci., 55:629-34, 1994). Exendin-3 and exendin-4 were reportedly found to stimulate CAMP production in, and amylase release from, pancreatic acinar cells (Malhotra, R., et al., Regulatory Peptides, 41:149-56, 1992; Raufman, et al., J. Biol. Chem. 267:21432-37, 1992; Singh, et al., Regul. Pept. 53:47-59, 1994). Additionally, exendin-4 has a significantly longer duration of action than GLP-1. For example, in one experiment, glucose lowering by exendin-4 in diabetic mice was reported to persist for several hours, and, depending on dose, for up to 24 hours (Eng J. Prolonged effect of exendin-4 on hyperglycemia of db/db mice, Diabetes 1996 May; 45(Suppl 2):152A (abstract 554)). Based on their insulinotropic activities, the use of exendin-3 and exendin-4 for the treatment of diabetes mellitus and the prevention of hyperglycemia has been proposed (Eng, U.S. Pat. No. 5,424,286).
The results of an investigation of whether exendins are the species homolog of mammalian GLP-1 was reported by Chen and Drucker who cloned the exendin gene from the Gila monster (J. Biol. Chem. 272(7):4108-15 (1997)). The observation that the Gila monster also has separate genes for proglucagons (from which GLP-1 is processed), that are more similar to mammalian proglucagon than exendin, indicates that exendins are not merely species homologs of GLP-1.
To date, agents that serve to delay gastric emptying have generally found a place in medicine as diagnostic aids in gastrointestinal radiological examinations. For example, glucagon is a polypeptide hormone that is produced by the alpha cells of the pancreatic islets of Langerhans. It is a hyperglycemic agent that mobilizes glucose by activating hepatic glycogenolysis. It can to a lesser extent stimulate the secretion of pancreatic insulin. Glucagon is used in the treatment of insulin-induced hypoglycemia, for example, when administration of glucose intravenously is not possible. However, as glucagon reduces the motility of the gastrointestinal tract it is also used as a diagnostic aid in gastrointestinal radiological examinations. Glucagon has also been used in several studies to treat various painful gastrointestinal disorders associated with spasm. Daniel, et al. (Br. Med. J., 3:720, 1974) reported quicker symptomatic relief of acute diverticulitis in patients treated with glucagon compared with those who had been treated with analgesics or antispasmodics. A review by Glauser, et al. (J. Am. Coll. Emergency Physns, 8:228, 1979) described relief of acute esophageal food obstruction following glucagon therapy. In another study, glucagon significantly relieved pain and tenderness in 21 patients with biliary tract disease compared with 22 patients treated with placebo (M. J. Stower, et al., Br. J. Surg., 69:591-2, 1982).
Methods for regulating gastrointestinal motility using amylin agonists are described in commonly owned International Application No. PCT/US94/10225, published Mar. 16, 1995.
Methods for regulating gastrointestinal motility using exendin agonists are described in commonly owned U.S. patent application Ser. No. 08/908,867, filed Aug. 8, 1997 entitled “Methods for Regulating Gastrointestinal Motility,” which application is a continuation-in-part of U.S. patent application Ser. No. 08/694,954, filed Aug. 8, 1996.
Methods for reducing food intake using exendin agonists are described in commonly owned U.S. patent application Ser. No. 09/003,869, filed Jan. 7, 1998, entitled “Use of Exendin and Agonists Thereof for the Reduction of Food Intake,” which claims the benefit of U.S. Provisional Application Nos. 60/034,905 filed Jan. 7, 1997, 60/055,404 filed Aug. 7, 1997, 60/065,442 filed Nov. 14, 1997 and 60/066,029 filed Nov. 14, 1997.
Novel exendin agonist compounds are described in commonly owned PCT Application Ser. No. PCT/US98/16387 filed Aug. 6, 1996, entitled “Novel Exendin Agonist Compounds,” which claims the benefit of U.S. Patent Application Ser. No. 60/055,404, filed Aug. 8, 1997.
Other novel exendin agonists are described in commonly owned PCT Application Serial No. PCT/US98/24210, filed Nov. 13, 1998, entitled “Novel Exendin Agonist Compounds,” which claims the benefit of U.S. Provisional Application No. 60/065,442 filed Nov. 14, 1997.
Still other novel exendin agonists are described in commonly owned PCT Application Serial No. PCT/US98/24273, filed Nov. 13, 1998, entitled “Novel Exendin Agonist Compounds,” which claims the benefit of U.S. Provisional Application No. 60/066,029 filed Nov. 14, 1997.
Other recent advances in exendin related technology are described in U.S. Provisional Patent Application Ser. No. 60/075,122, filed Feb. 13, 1998, entitled “Inotropic and Diuretic Effects of Exendin and GLP-1” and in U.S. Provisional Patent Application Ser. No. 60/116,380, filed Jan. 14, 1998, entitled “Novel Exendin Agonist Formulations and Methods of Administration Thereof”.
Polyethylene glycol (PEG) modification of therapeutic peptides and proteins may yield both advantages and disadvantages. While PEG modification may lead to improved circulation time, reduced antigenicity and immunogenicity, improved solubility, resistance to proteolysis, improved bioavailability, reduced toxicity, improved stability, and easier formulation of peptides (See, Francis et al., International Journal of Hematology, 68:1-18, 1998) problems with PEGylation in most cases is substantial reduction in bioactivity. Id. In addition, most methods involve use of linkers that have several types of adverse effects including immunogenicity, instability, toxicity, and reactivity. Id.
Glucagonoma (tumor of glucagon-secreting cells) produces, in addition to glucose intolerance, a skin condition, necrolytic migratory erythema. This is a raised scaly red rash, sometimes blistering and eventually crusting, localized to the face, abdomen, extremities and perineum. It can also be associated with inflamation of the tongue and mouth, and diseased nails and thinning of the hair. The condition is reported to respond to octreotide, a glucagonostatic hormone analog. The compounds described herein are also useful as glucagonastatic agents and thus in the treatment of this disease, which was was first described in 1966 (Kaplan, L. M. Endocrine Tumors of the Gastrointestinal Tract and Pancreas. Ch 262, pl392: In Harrison's Principles of Internal Medicine, 12th Edition. McGraw-Hill Inc, New York, 1991). The compounds described herein that are useful for lowering glucagon levels and/or suppressing glucagon secretion include exendin, exendin agonists, and modified exendins and exendin agonists and related formulations, and dosage formulations.
The contents of the above-identified articles, patents, and patent applications, and all other documents mentioned or cited herein, are hereby incorporated by reference in their entirety. Applicants reserve the right to physically incorporate into this application any and all materials and information from any such articles, patents, patent applications, or other documents mentioned or cited herein.